Approximately 8:00 Post Meridian. Vacaville, California. Was on evening jog, the same route I take every night. Large, light gray disc. Looked maybe 500 feet wide. About 2,000 feet above surface. emitted a soft green glow from the edges. Hovered in placed for about 53 seconds. Suddenly accelerated due north. At least 2,000 mph. I am a former air force f-15 pilot. I know my planes. This was not of this world.